Actually, this is number 6. In the US they clumped together Dynasty Warriors with a previous fighting game when they were in fact two different games entirely. DW2 in the US, effectively, is in reality the first Dynasty Warriors. Koei has been making games based on the Romance of The Three Kingdoms stories for absolute yonks, and there's a series called just that on SNES at the earliest I believe. Strategy games Kessen and Kessen 2 on the PS2 also tie into the same mythology/folklore.

I should probably fact check some of this because I'm speaking from what I remember right now, but yeah, that's at least roughly accurate. :)

But yeah, counting the bazillion spinoffs on the Dynasty Warriors (or Something Musou as they're called in japan) template, they've accumulated quite a few. On the surface they're identical, in actuality they're similar but feel pretty significantly different.

There's a lot of fanservice surrounding all editions of these games, but I also think it fills an incredibly narrow brawler-esque niche. People claim Devil May Cry is where the Streets of Rages and Final Fights went, but the almost hypnotic rythm and the steady dial-a-combo repetition of the Dynasty Warriors games coupled with a casual chat-over-what-you're-doing co-op mode hits those notes more faithfully. For better or worse, as it were.